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Scientific Proceedings, Royal Dublin Society. 



last — the triple roller system as it is generally called. It is a 

 fault that is very common with apparatus that is the best, viz. it 

 is very expensive to make, mainly because the wall-plates, having 

 to be planed of the peculiar form described, are really portions of 

 cones, and cannot be planed in any ordinary planing machine. A 

 special machine had to be made, and as this machine has practi- 

 cally to be re-made for every different radius of dome constructed, 

 the cost is very great. I have therefore designed a new form wliich, 

 while equally efficient, can be constructed at a considerably less 

 cost (see figs. 9 and 10). 



Fig. 9. 



Fig. 10. 



In this new form of revolving gearing, the wall-plate " W " 

 consists of a cast-iron ring, something of the form of the letter TJ, 

 with any necessary flanges for attachment to the wall. The top 

 surface of the two vertical ribs, only, requires to be planed to a true 

 surface. On these two planed edges roll the axes of a set of live 

 rollers " L," on which rollers rolls the true cast-iron plate which 

 forms the base of the dome " S " (see fig. 9). 



The rollers forming the live ring are kept in their proper posi- 

 tions and distances from one another by a set of light wrought- 

 iron frames (see fig. 10) coupled one to another by chains. It is 

 preferable that the rollers be coupled together in pairs, as this 

 ensures them against twisting, and thus avoids unnecessary fric- 

 tion on the flanges. It will be observed that in this form the 



